Alternating-current magnet.



T. E. BARNUM.

ALTERNATING CURRENT MAGNET. APPLICATION TILED APB.16, 1905.

Patented Dec. 1, 1908.

T. E. BARNUM.

ALTEBNATING CURRENT MAGNET. urmculon FILED APR. 15, 1905.

Patented Dec. 1, 1908.

Z SHEETS-SHEET 2.

UNITED STATES V PATENT OFFICE.

THOMAS E. BARNUM, Ol L\I.IL\\"AUKEE, WISCONSIN, ASSIGNOR TOGUTLER-HAMMER MANU- FAGlURlNG UOMPAN'Y, O11 .lllLlv AUliEE, WISCONSIN, AOOltPOlEtATlTlON Ol WISCONSIN.

ALTERNATING-GURRENT MAGNET.

Specification 01" Letters Patent.

Application filed April 15, 1905.

Patented Dec. 1, 1908.

Serial No. 255,713.

To all whom. it may concern:

Be it known that l, 'llnoaus E. Barman, a citizen of the United States,residing at Milwaukee, in the county of Milwaukee and State ofl'Visconsin, have invented new and useful Improvements in.Alternating-Current.- Magnets, of which the following is a lull, clear,concise, and exact description, reference being had to the accompanyingd *awing, forming a part of this s1 )ecifica lion.

My invention relates to improvements in magnets, for use on alternatingcurrent circuits, my object being to provide a magnet which will besimple in constructioi'i, and at the same time self-protecting fromoverheating after the magnet has attracted. its armature.

A further object of my invention is to provide a pulling magnet in whichwhen the current is first admitted to the windings thereof, a largeamount ot current will flow and consequently exert a strong pull on thearmatm'e but after the armature has been attracted to the coil, theamount of current :llowiug through the coil is greatly reduced.

A, still further object of my invention is to provide means "forconnecting the armature of the magnet to a switch whereby a hammer blowwill be given in opening and closing the switch to more readily operatethe same.

I have illustrated the preferred embodiment of my invention inv theaccompanying drawings, in which:

Figure 1 is a front. elevation of my device showing the same operating aswitch; Fig. 2, is side elevation of the same; Fig. 3 is 2. bottom planview of my device; Fig. i is a front elevation of a modification off mydevice; Fig. 5 is a side elevation thereof, and Fig. 6 .is a bottomview.

in one torm oil? the practical embodiment of my invention, upon asuitable base 1, made of insulating material, usually in the form of amarble slab is mounted asolenoid winding of the usual type which issurrounded by and supported within an iron shroud 3 having projectinglugs at, through which screws are passed to secure the same to the base1.. Suitable screws pass through the lower side of the shroud to adjustably support the coil upon the same. The shroud 3, it will be noted,is not con tinuous and on its underside is cut a ay to form the airspace 6. A core or plunger 7 is adapted to operate in the coil and beraised thereby when. the current is admitted to the windings oi? thecoil.

The air gap 6 is so proportioned that when the phmger or core is in itslowermostposition the passage of current through the coil will not besubstantially atlectedthat is, the variable air gap in the magneticciron it is comparatively large, and the fixed air gap is of suchproportion that; when the plunger or core is down the self-induction ofthe magnet will not be affected and the current will pass. As thevariable air gap, however, decreases, the fixed air gap 6 be comesrelatively more important, and when the plunger is in its raisedposition the fixed air gap is practically the only air gap in themagnetic circuit and prevents the self-induction oi the coil :lrombecoming so high as to prevent the passage of sutiicient current tomaintain the core in its raised position. By thus so proportioning thefixed air gap 6 with respect to the variable air gap formed by theplunger or core, when the plunger or core is at its lowest position theself-induction oi. the coil. willv be only sutlicient to prevent currentto pass through the coil which will be so great. as to heat the same butwill. not prevent the passage of suFicient current to raise the core;but when the plunger is at its uppermost position, only a sutficientamount of current will be permitted to pass through the coil to energizethe magnet sutliciently to maintain the plunger firmly in its raisedposition; and it is thus by so proportionil'ig the tixed air gap withrespect to the variable air gap that I am enabled to accomplish theobject of my invention and prevent the self induction of the magnet frombeing too high when the plunger is in its uppermost position, andprevent the fixed air gap when the plunger is in its lowermost positionfrom substantially a'tl ecting the magnetic circuit.

Projecting from the base 1 below the solenoid is a pin 8 upon which issuitably pivoted a switch arm 9 having its opposite end flattened as atit) and adapted, when in a closed position to engage between thebifurcations ll of a contact plate and be held in a closed positionthereby. In order that this plate may be mounted in line with the outerend of the switch arm, it is preferably secured by means of a screw 12upon the outer end of a pin 13 projecting from the base. The screw 12passes through the pin and a nut 14: upon the upper end thereof holds inposition a spring 15 which extends below the lower ends of contact clips11 so that the circuit is broken at this point last and the spring takesthe arc resulting from opening the switch with the current passing. Thedownward movement of the switch arm is limited by a stop 16 secured uponthe base 1. i

The central portion or the switch arm is enlarged and has formed thereina slot 17 through which is adapted to pass a rod 18 secured at its upperend to the core or plunger 7. A nut 19 is screwed upon the lower end ofthe rod and is adapted when the rod is raised by the core or plunger 7to en age the switch arm and move the same. ii set nut 20 is alsoprovided upon the lower end of the rod to prevent the nut 19 from beingdisplaced after it has once been adjusted. i"

In operation, assuming the switch to be open when the current has beenadmitted to the windings of the coil 2, the self-induction set up by thewires or" the magnetized coil is so small, due to the gap in themagnetic circuit and to the external air gaps 6, that a large amount ofcurrent will flow through the coil and exert a strong pull upon the coreto raise the same. is the nut 19 will not engage the switch arm untilafter the core has been started in its upward. movement, a hammer blowwill be delivered to the switch arm and the same will be readily raisedby the core or plunger until the arm makes contact with the contactplate 11 and is engaged by the spring 15. is the core is sucked up intothe coil. the air gap in the magnetic circuit will be decreased and thesell induction set up by the coils accordingly increased. ll hen thecore has reached its uppermost position, the magnet circuit is so nearlyclosed that t self induction is so great that the amount of currentlimving through the coil is reduced to just enough to maintain the corein the raised position. In practice the current may be reduced to as lowas one-tenth the amount which flowed when the plunger was in itslowermost position. It will be noted that due to the fact that theswitch arm is supported in a closed position by the spring very littlecurrent must pass through the winding of the coil as only sullicientforce must be exerted by the coil after the switch arm is closed. tomaintain its own core in raised position. hen the switch is to be openedby cutting oll the current through the coil the plunger will bepermitted to drop by its own weight and deliver a hammer blow upon theswitch a 111 releasing the same from the retaining spring and permittingthe arm to drop to its lowermost position.

In my Figs. a to 6, l have shown a slight modification of my device inwhich an insulating plate 21 is secured at right angles 2 to the baseand maintained in position by lscrews passing through the plate andscrewing into the iron shroud 3 of the magnet. This plate forms asupport. for the contact 11, a bolt 93 passing through said. 5 contactand plate and held in position by i nuts 2a. The spring 15 is alsosupported l and held in position by the bolt A de' pending support 25 isalso secured to said plate by a bolt 2t) and nuts 27 and to the lowerend of this su port is pivoted the switch arm, 9.

Having thus described myinventiomwhat I claim as new and desire tosecure by Letters Patent is:-

1. An alternating current magnet having an air gap in the magneticcircuitindependent 01'? that formed between the magnetic circuit and themovable armature, and so proportioned that when the armature is in oneposition, the self induction of the magnet {will permit the passage ofcurrent there 1 through to actuate the armature, but when l the armatureis in another position, the selfinduction of the magnet will increase topermit only sullicientcurrent to pass through the magnet to maintain thearmature in its second position.

2. in an alternating current magnet the combination with the magneticcoil of an iron shroud surrounding said coil having an air gap formedtherein so proportioned that y when the armature of the magnet in one 1position, the sell induction of the magnetic l coil will permit thepassage of current therethrough to attract the armature, but when thearmature is attracted, only suliicient current is permitted to passthrough the magnet to maintain the armature in its second position.

Bin alternating current magnet having a variable air ga p and anon-variable air gap of the magnetic circuit, said air gaps being soproportioned that when the armature is in one position. the ellect otthe variable air gap upon the magnet is modified to a minimum, extent.by the non- 'ariable air gap, but when the variable air gap is thesmallest. the non-\'ariable air gr) will permit only su .'icient currentto pa: through the magnet to maintain the armature in its finalposition.

l. In an alternating current magnet the combination oi the solenoidwinding, of a core or plunger operated thereby, an external magneticcircuit associated with said winding and provided with a fixed air gap;said air gap being so proportioned that when the core or plunger is inone position the air gap in the magnetic circuit formed by said plungerreduces the self-induction of the coil to a minimum, but when the coreor plin 'er is in a second. position the self inouction of the coil isso allected that only suflieient current will be permitted to passtherethrough to inaintaii'i the core in. its final position.

In an alternating current magnet the combination with a solenoidWinding, of a core or plunger operated thereby, and forming part of amagnetic circuit associated with the solenoid, said magnetic circuitbeing provided With a fixed and a variable air gap, the utter being soproportioned that when the variable air gap is greatest, the effect ofthe fixed air gap upon the self induction of the magnet is reduced to aminimum, but when the variable air gap is smallest, the fixed air gapwill so affect the selfinduction of the coil that only sutlicientcurrent may pass therethrough to maintain the core or plunger in itsfinal position.

0. In an alternating current magnet the combination With. a solenoidwinding, of a core or plunger operated by said winding, and an ironshroud surrounding said Winding having an air gap therein, said air gapbeing so proportioned that when the core or plunger is in one position,the effect of the air gap upon the self induction of the coil is reducedto a minimum, but when the core or plunger is in a second position, theself induction of the coil Will be so aflected that only suliicientcurrent inay pass through the coil to hold the core or plunger in itssecond position.

In Witness whereof, I have hereunto sub- 7 scribed my name in thepresence of two witnesses.

THOMAS E. BARNUM. Witnesses F. S. VVILLWIT, L. P. COULTEK.

